Application of photon detectors in the VIP2 experiment to test the Pauli Exclusion Principle

TL;DR

The paper discusses the use of advanced photon detectors in the VIP2 experiment to improve the testing of the Pauli Exclusion Principle's validity by searching for forbidden electronic transitions in copper.

Contribution

It introduces the implementation of Silicon Drift Detectors and active scintillator shielding in VIP2 to enhance sensitivity in PEP violation tests.

Findings

Expected improvement of two orders of magnitude in upper limit for PEP violation

Use of Silicon Drift Detectors enhances X-ray detection capabilities

Active shielding reduces background noise

Abstract

The Pauli Exclusion Principle (PEP) was introduced by the austrian physicist Wolfgang Pauli in 1925. Since then, several experiments have checked its validity. From 2006 until 2010, the VIP (VIolation of the Pauli Principle) experiment took data at the LNGS underground laboratory to test the PEP. This experiment looked for electronic 2p to 1s transitions in copper, where 2 electrons are in the 1s state before the transition happens. These transitions violate the PEP. The lack of detection of X-ray photons coming from these transitions resulted in a preliminary upper limit for the violation of the PEP of $4.7 \times 10^{-29}$. Currently, the successor experiment VIP2 is under preparation. The main improvements are, on one side, the use of Silicon Drift Detectors (SDDs) as X-ray photon detectors. On the other side an active shielding is implemented, which consists of plastic scintillator bars read by Silicon Photomultipliers (SiPMs). The employment of these detectors will improve the upper limit for the violation of the PEP by around 2 orders of magnitude.